1. Field of the Invention
The present invention is broadly concerned with a method and apparatus for the continuous production of sterile pelleted feed products, such as those used for the feeding of cattle, hogs, poultry and other livestock. More particularly, it is concerned with such a method and apparatus making use of an extruder device equipped with a unique pelleting head adjacent the outlet end of the extruder barrel and operable for receiving material directly from the extruder barrel and forming the same into sterile, self-sustaining pelleted bodies. The invention also comprehends the final pelleted bodies which have a novel combination of properties important in the context of livestock feeds.
2. Description of the Prior Art
Livestock feeds have long been produced through use of conventional pellet mills. In such methods, the starting feed ingredients, together with optional binders, are fed to the inlet of the pellet mill and are formed into self-sustaining bodies. A common problem associated with such feeds is that they lack requisite sterility. This factor is of increasing concern in a wide variety of feeds, but especially in poultry feeds where salmonella is a significant problem. Furthermore, prior pelleted feeds are characterized by no more than about 40% gelatinization the starch fractions thereof, and with less than 70% of the protein contents being denatured, which present problems of digestibility.
It has also been known in the past to process feed materials using a extrusion cooker. This technique produces a fully cooked feed product, but typically results in an expanded cellular structure in the feeds and consequent low bulk densities and specific gravities.
Finally, it has also been proposed to initially process feed ingredients using an extrusion cooker, o followed by grinding of the extrudate and subsequent passage thereof through a separate, conventional pellet mill. This is of course a relatively expensive proposition, requiring both an extruder and a pellet mill, as well as intervening processing equipment. As such, the economics of such a system are unfavorable.